Exhaust component with flexible membrane

ABSTRACT

A vehicle exhaust system includes an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity. At least one hole is formed in the exhaust component to extend through the wall of the exhaust component from the outer surface to the inner surface. A membrane is configured to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.

TECHNICAL FIELD

This disclosure relates generally to an exhaust component having an opening formed within a wall that is covered with a membrane that is moveable in response to pressure fluctuations to reduce noise.

BACKGROUND

Vehicle exhaust systems direct exhaust gases generated by an internal combustion engine to the external environment. These systems are comprised of various components such as pipes, converters, catalysts, filters, etc., which are used to reduce emissions. The overall system and/or the components are capable of generating undesirable noise as a result of resonating frequencies. Different approaches have been used to address this issue. For example, components such as mufflers, resonators, valves, etc., have been incorporated into exhaust systems in an attempt to attenuate certain resonance frequencies generated by the exhaust system. Including additional components can be expensive and increases weight, while also introducing new sources for noise generation.

SUMMARY

A vehicle exhaust system according to an exemplary aspect of the present disclosure includes, among other things, an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity. At least one hole is formed in the exhaust component to extend through the wall of the exhaust component from the outer surface to the inner surface. A membrane is configured to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.

In a further non-limiting embodiment of the foregoing vehicle exhaust system, the membrane is made from a flexible material.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the flexible material can withstand temperatures within a range of 500-850 degrees Celsius.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane is impermeable.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the wall is impermeable.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole is positioned at a pressure anti-node.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole comprises a plurality of holes that are each positioned at a pressure anti-node and which are each covered by a corresponding membrane.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the exhaust component comprises a pipe having an overall pipe length extending from a first pipe end to a second pipe end, and wherein the at least one hole is positioned at a pressure anti-node location that is approximately 25%, 50%, or 75% of the overall pipe length.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole comprises a plurality of holes that are each positioned at one of the pressure anti-node locations.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, each hole is covered by a separate membrane.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane has both stiffness and damping and the pressure fluctuations cause the membrane to move and absorb energy from an oscillating wave resulting in lower downstream pressure oscillations.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the stiffness and damping are adjusted such that a resonant frequency of the membrane is tuned to provide maximum suppression of the downstream pressure oscillations.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane is made from a flexible material that is impermeable and elastically deformable.

In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the outer surface of the wall and the membrane are directly exposed to external atmosphere.

A method according to still another exemplary aspect of the present disclosure includes, among other things: providing an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity; forming at least one hole in the exhaust component to extend through the wall from the outer surface to the inner surface; and positioning a membrane to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.

In a further non-limiting embodiment of the foregoing method, the method includes forming the membrane from a flexible material that is impermeable, elastically deformable, and can withstand temperatures within a range of 500-850 degrees Celsius.

In a further non-limiting embodiment of any of the foregoing methods, the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.

In a further non-limiting embodiment of any of the foregoing methods, the method includes positioning the at least one hole at a pressure anti-node.

In a further non-limiting embodiment of any of the foregoing methods, the at least one hole comprises a plurality of holes, and including positioning each hole at a pressure anti-node, covering each hole with a separate membrane, and adjusting stiffness and damping of the membrane such that a resonant frequency of the membrane is tuned to provide maximum suppression of downstream pressure oscillations.

The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE FIGURES

The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows:

FIG. 1 schematically illustrates one example of an exhaust system.

FIG. 2A illustrates a side view of a pipe including a hole covered by a flexible membrane.

FIG. 2B is a perspective view of the membrane of FIG. 2A and one example of a mount that is used to attach the membrane to the pipe.

FIG. 3 schematically illustrates possible pressure anti-node mounting locations of the membrane along the pipe.

FIG. 4A illustrates a side view of the membrane at a pressure anti-node location.

FIG. 4B schematically illustrates a mechanical analogy of the membrane at the pressure anti-node location of FIG. 4A.

FIG. 5 schematically illustrates an example configuration of a muffler with a membrane.

FIG. 6A schematically illustrates an example of a flexible membrane comprising a corrugated diaphragm.

FIG. 6B is a side view of the diaphragm of FIG. 6A.

DETAILED DESCRIPTION

This disclosure details an exemplary exhaust component having an opening formed within a wall that is covered with a membrane, which is moveable in response to pressure fluctuations to reduce resonance noise.

FIG. 1 shows a vehicle exhaust system 10 that conducts hot exhaust gases generated by an internal combustion engine 12 through various downstream exhaust components 14 to reduce emissions and control noise as known. The exhaust components 14 can include diesel oxidation catalysts (DOC), selective catalytic reduction (SCR) catalysts, particulate filters, mufflers, valves, exhaust pipes, etc. These components 14 can be mounted in various different configurations and combinations dependent upon vehicle application and available packaging space. Exhaust gases pass through the components 14 and are subsequently directed to the external atmosphere via a tailpipe 16, for example.

The exhaust system 10 includes at least one acoustic damping membrane 18 (shown schematically in FIGS. 2A-B) that dampens resonance frequencies generated during operation of the system 10. In one example, the acoustic damping membrane 18 is used in an exhaust component 20 having an outer surface 22 and an inner surface 24 that defines an internal exhaust component cavity 26. The inner surface 24 defines an exhaust gas flow path F. In this example shown, the exhaust component comprises a pipe 20.

At least one hole 28 is formed in the pipe 20 to extend through a thickness of a wall 30 of the pipe 20 from the outer surface 22 to the inner surface 24. The membrane 18 is formed from a flexible material and is configured to overlap the hole 28. The membrane 18 moveable relative to the wall 30 in response to pressure fluctuations. It should be understood that while the membrane 18 is shown as being used with a pipe 20, the membrane 18 could also be used in any of the various exhaust components 14 as needed, such as in a muffler or in a pipe that is mounted within a muffler, for example. FIG. 5 shows an example of the membrane 18 as utilized with a muffler 14 a.

As discussed above, the membrane 18 is made from a flexible material and is impermeable such that no fluids, i.e. liquid or gas, can pass through the membrane 18. Depending on the application location, the maximum temperature requirements for the flexible membrane 18 could be anywhere from 500-850° C. For lower temperature applications, e.g. less than 600° C., the flexible membrane 18 be made using a copper-beryllium alloy. For applications above 600° C., a stainless-steel membrane, made from 304SS for example, could be used. Obviously, other materials may be used as appropriate. For colder applications, e.g. less than 260° C., silicone could be used for example.

FIGS. 6A-6B show an example of a corrugated diaphragm 56 that could be used as the flexible membrane element. In one example, the corrugated diaphragm 56 includes an outermost peripheral edge 58 and a flat center portion 60. A plurality of troughs 62 and protrusions 64, which alternate with each other, are formed between the outermost peripheral edge 58 and the flat center portion 60.

In one example, the wall 30 comprises a rigid structure that has a first compliance and the membrane 18 comprises a flexible structure that has a second compliance that is greater than the first compliance. The membrane 18 elastically deforms in response to pressure changes within the internal exhaust component cavity 26. As such, the membrane 18 has a rest position, where the membrane 18 lies generally flat and/or conforms to a shape of the wall 30 along the outer surface 22, and an active position where the pressure fluctuations within the exhaust component cause portions of the membrane 18 to move relative to the wall 30, e.g. expand and/or contract, before returning the rest position.

The outer surface 22 of the wall 30 and an outer surface 36 of the membrane are both directly exposed to external atmosphere. As discussed above, the membrane 18 is made from a flexible material that is impermeable. The wall 30 of the exhaust component 20 is also impermeable. As such, none of the exhaust gas flowing through the exhaust component 20 can leak out or escape to the external atmosphere. This also prevents any fluid or debris from getting into the exhaust component 20 via the hole 28.

In one example, the at least one hole 28 comprises a single or only hole 28 in the pipe 20. In another example, the at least one hole 28 comprises a plurality of holes 28 that are formed within the pipe 20. In one example, the hole 28 is positioned at a pressure anti-node. When multiple holes 28 are provided, each hole 28 can be positioned at a pressure anti-node, with each hole 28 being covered by a separate membrane 18.

FIG. 3 shows an example where the pipe 20 extends along a central axis A from a first pipe end 32 to a second pipe end 34. In one example, the at least one hole 28 comprises the only hole 28 in the pipe 20 that extends entirely through the wall 30. The pipe 20 is defined by an overall pipe length L from the first pipe end 32 to the second pipe end 34. In one example, the single hole 28 is positioned at a location that is approximately 50% of the pipe length, i.e. the hole 28 is positioned generally at an equal distance from each of the first pipe end 32 and the second pipe end 34. This hole location is very effective because it is located near an acoustic standing wave pressure anti-node (maximum pressure point) location 38 (FIG. 4A). For example, in a first mode comprising a ½ wave mode, the hole 28 is located where it is at a position that is approximately 50% of the overall length L from either the first 32 or second 34 pipe end.

In another example, the at least one hole comprises only a first hole 28 and a second hole 28′ that extend entirely through the wall 30. In this example, the first hole 28 is positioned at the location that is approximately 50% of the pipe length L and the second hole 28′ is positioned at location that is approximately 75% of the pipe length from one end or 25% from an opposite end as optionally indicated at one of two possible locations in FIG. 3. This position generally corresponds to a pressure anti-node for the full wave mode. Each hole 28, 28′ would be covered by one membrane 18 formed of the flexible material. In another example, more than two holes 28 could also be provided.

FIG. 4A shows a schematic representation of the acoustic damping membrane 18. It should be understood that the membrane 18 could be configured to cover the hole 28 at the external surface 22 or the internal surface 24 of the pipe 20. When mounted to the internal surface 24, the membrane 18′ is protected from damage from rocks and other debris. When mounted to the external surface 22, as shown in FIG. 4, the membrane 18 is separated from high velocity gas flow which further improves acoustic performance.

As shown in FIG. 2B, the membrane 18 comprises a continuous piece of flexible material, i.e. a single piece of material, which is cut or shaped to a desired size. FIG. 2B also shows one example mounting method to attach the membrane 18 to the pipe 20. In this example, a frame 40 is used to attach the membrane 18 to the outer surface 22 of the pipe 20. In one example, the frame 40 comprises a polygonal shape, e.g. square, rectangular, etc. Optionally, other shapes such as circular, oval, elliptical, curvilinear, etc. could also be used. In the example shown, the frame 40 is rectangular and has an open center area 42 that is surrounded by a plurality of outer edges 44. The edges 44 are attached to the outer surface 22 of the pipe 20 such that outer peripheral edges 48 of the membrane 18 are sandwiched or clamped between an inner surface 46 of the edges 44 and the outer surface 22 of the pipe 20. The edges 44 can be welded or brazed to the pipe 20, for example. A center area of the membrane 18 overlaps the hole 28, and the open center area 42 of the frame 40 overlaps the center area of the membrane 18. As such, the center area of the membrane 18 is free to move/deform elastically in response to pressure fluctuations in order to reduce resonance noise.

For a configuration with a flexible membrane 18 formed from a thin stainless steel diaphragm, the membrane 18 may be welded to the adjoining pipe 20, for example.

FIG. 4B schematically illustrates a mechanical analogy of the membrane 18 at the pressure anti-node location 38 of FIG. 4A. As shown, the membrane 18 has both stiffness 50 and damping 52 and the pressure fluctuations cause the membrane 18 to move and absorb energy from an oscillating wave 54 resulting in lower downstream pressure oscillations. In one example, the stiffness 50 and damping 52 are adjusted such that the resonant frequency of the membrane is tuned to provide maximum suppression of the downstream pressure oscillation.

The subject disclosure uses one or more flexible patches or membranes 18 on a pipe 20 whose resonances are to be suppressed. The membrane 18 is elastic and impermeable such that exhaust gas does not leak out under a body of the vehicle, which avoids any possibility of undesirable odor, CO intrusion, high thermal effects, etc. The flexible membranes 18 are located at the pressure anti-node locations 38 to provide maximum effect. Several such flexible membranes 18 can be provided in order to address several pipe modes or one pipe mode more effectively.

The compliance of the flexible membrane 18 is much greater than that of the adjoining pipe 20. As such, the flexible membrane 18 will deform in reaction to the changing pressure. Additionally, there is no increased radiated noise or flow noise, or back pressure compared to prior solutions that utilize a porous member open to the atmosphere combined with a deflector to eliminate leakage of the exhaust gas.

Although a specific component relationship is illustrated in the figures of this disclosure, the illustrations are not intended to limit this disclosure. In other words, the placement and orientation of the various components shown could vary within the scope of this disclosure. In addition, the various figures accompanying this disclosure are not necessarily to scale, and some features may be exaggerated or minimized to show certain details of a particular component.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims. 

what is claimed is:
 1. A vehicle exhaust system comprising: an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity; at least one hole formed in the exhaust component to extend through the wall of the exhaust component from the outer surface to the inner surface; and a membrane configured to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.
 2. The vehicle exhaust system according to claim 1, wherein the membrane is made from a flexible material.
 3. The vehicle exhaust system according to claim 2, wherein the flexible material can withstand temperatures within a range of 500-850 degrees Celsius.
 4. The vehicle exhaust system according to claim 1, wherein the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.
 5. The vehicle exhaust system according to claim 1, wherein the membrane is impermeable.
 6. The vehicle exhaust system according to claim 5, wherein the wall is impermeable.
 7. The vehicle exhaust system according to claim 1, wherein the at least one hole is positioned at a pressure anti-node.
 8. The vehicle exhaust system according to claim 1, wherein the at least one hole comprises a plurality of holes that are each positioned at a pressure anti-node and which are each covered by a corresponding membrane.
 9. The vehicle exhaust system according to claim 1, wherein the exhaust component comprises a pipe having an overall pipe length extending from a first pipe end to a second pipe end, and wherein the at least one hole is positioned at a pressure anti-node location that is approximately 25%, 50%, or 75% of the overall pipe length.
 10. The vehicle exhaust system according to claim 9, wherein the at least one hole comprises a plurality of holes that are each positioned at one of the pressure anti-node locations.
 11. The vehicle exhaust system according to claim 10, wherein each hole is covered by a separate membrane.
 12. The vehicle exhaust system according to claim 1, wherein the membrane has both stiffness and damping and the pressure fluctuations cause the membrane to move and absorb energy from an oscillating wave resulting in lower downstream pressure oscillations.
 13. The vehicle exhaust system according to claim 12, wherein the stiffness and damping are adjusted such that a resonant frequency of the membrane is tuned to provide maximum suppression of the downstream pressure oscillations.
 14. The vehicle exhaust system according to claim 1, wherein the membrane is made from a flexible material that is impermeable and elastically deformable.
 15. The vehicle exhaust system according to claim 14, wherein the outer surface of the wall and the membrane are directly exposed to external atmosphere.
 16. A method comprising: providing an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity; forming at least one hole in the exhaust component to extend through the wall from the outer surface to the inner surface; and positioning a membrane to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.
 17. The method according to claim 16, including forming the membrane from a flexible material that is impermeable, elastically deformable, and can withstand temperatures within a range of 500-850 degrees Celsius.
 18. The method according to claim 16, wherein the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.
 19. The method according to claim 16, including positioning the at least one hole at a pressure anti-node.
 20. The method according to claim 16, wherein the at least one hole comprises a plurality of holes, and including positioning each hole at a pressure anti-node, covering each hole with a separate membrane, and adjusting stiffness and damping of the membrane such that a resonant frequency of the membrane is tuned to provide maximum suppression of downstream pressure oscillations. 